<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .c1{color: green;}
        .c1[hah='1']{color: red}
    </style>
</head>
<body>
    <div class="c1" hah="1">11</div>
    <div class="c1">22</div>
    <div class="c1">11</div>
</body>
</html>